High-frequency electron tubes



April 1966 FUMlO HOSHINO ETAL 3,246,195

HIGH-FREQUENCY ELECTRON TUBES Filed March 21, 1963 2 Sheets-Sheet 1Fig.l

Fig. 3

INVENToRS Fumm Ho5H No YOSHIO mURHTH April 1966 FUMIO HOSHINO ETAL3,246,195

HIGH-FREQUENCY ELECTRON TUBES Filed March 21, 1963 2 Sheets-Sheet 2 Fig.2

INvENToRS Fumlo HOSHINO Yosmo muRnTH HTTaRNEY United States Patent3,246,195 HIGH-FREQUENCY ELECTRON TUBES Fumio Hoshino and Yoshio Murata,Mohara-shi, Chiba, Japan, assignors to Hitachi, Ltd., Tokyo, Japan, acorporation of Japan Filed Mar. 21, 1963, Ser. No. 267,015 Claimspriority, application Japan, Apr. 17, 1962, 37/ 18,727 Claims. (Cl.313-240) The present invention relates to high-frequency electron tubesfor use in grounded grid circuits.

In the 'past, miniature type receiving tubes have involved a deficiencythat, in high-frequency operation, as the frequency increases the gainof such tubes is gradually reduced, therefore the tube operation becomesunstable and finally the tube itself becomes incapable of functioning asan amplifier. The reduction in gain in high-frequency operation islargely attributable to the following factors: (1) the increase in inputand output conductances due to the self-inductance of lead-in wires forthe electrodes; (2) the increase in ohmic loss in the leads due to theskin effect; and (3) the increase in high-frequency dielectric loss inthe stem insulation. Also, the unstable operation is caused by the factthat the inductance of the grid lead makes the grounding of the gridincomplete and that the input and output circuits are coupled throughthe interelectrode capacitance so that part of the output is fed back tothe input.

Previously, for the purpose of overcoming these diffi culties, variousways have been developed, for example, inner leads of minimized lengthsor multiple leads have been used to reduce the self-inductance of theleads. Also, a shield element has been inserted between a cathode and ananode to reduce the interelectrode capacitance therebetween for thepurpose of minimizing the capacity coupling between input and output.With miniature type receiving tubes, however, such measures as usingshortened inner leads and increasing leads in number are subject tostructural limitations and are naturally limited in their effect toreduce the inductance. A shield such as used in a conventional miniaturetube is in fact effective only to shield the cathode and anode but doesnot shield the connectors and inner leads connected to such electrodes.Hence, the shielding effect between the input and the output havenecessarily been incomplete.

Another way to avoid the above difficulties is the use of disc seal typetubes. This type of tube construction, however, involves a complicatedmanufacturing process not suitable for mass production and is veryexpensive beyond comparison with the miniature type tube construction.

The present invention has for its object to provide a high-frequencyelectron tube which is devoid of the above indicated deficiencies metwith conventional miniature type receiving tubes and which is easy tofabricate just like the latter.

Another object of the invention is to provide a highfrequency electrontube of the character described which is easy to assemble and is rigidin structure.

According to the present invention, a high-frequency electron tubecomprises a ceramic wafer, a grid lead plate extending through saidceramic Wafer centrally thereof and secured thereto, such as by brazing,and a shield plate secured to and electrically connected with said gridlead plate to shield between the cathode and cathode lead of the tube onthe one hand and the anode and anode lead thereof on the other.

These and other objects, features and advantages of the presentinvention will become apparent from the following description when takenin conjunction with the accompanying drawings, which illustrates oneembodiment of the invention and in which:

FIG. 1 is a perspective view, partly cut away, of the inner structure ofan electron tu-be embodying the invention;

FIG. 2 is an exploded view illustrating several components of the innerstructure; and

FIG. 3 an exterior View, partly cut away, of the miniature type electrontube according to the present invention.

Referring to the drawings, particularly to FIGS. 1 and 2, referencenumeral 1 designates a ceramic wafer having a slit centrally thereof andproperly spaced-apart circular apertures '3, 4, 5 and 6. These apertures3, 5, and 6 are disposed on one side of the slit 2 and the aperture 4 isdisposed on opposite sides of the slit 2, as clearly seen at the bottomportion of FIG. 2. A grid lead plate 7 is fitted through the slit 2formed in the wafer 1 and secured thereto in the conventional manner,such as, by brazing. Cathode pin 8, anode pin 9 and heater pins 10, 11are fitted through apertures 3, 4, 5 and 6 respectively and secured inplace as by brazing to form a stem structure. Numeral 12 designates ashield plate; 13 a frame grid; 14 a cathode; 15 an anode; 16 grid wires,and 20 a heater. Numerals 17, 17 designate respective mica sheetsarranged opposite to each other and formed with elongated slots a, b andc for the purpose of supporting the electrodes, as shown in FIG. 2.

In assembling, the cathode 14, frame grid 13 and anode 15 are fitted fortheir support in the slots in the mica sheets 17, 17', which in turn areinserted into slits d formed in the shield plate 12. The frame grid 13has on each side thereof spaced lugs 18 and 19, which are welded to theshield plate so that the frame grid is firmly held in place.

The shield plate 12 is thereafter welded to the grid lead plate 7 andfinally the cathode 14, anode 15 and heater 20 are connected to the pins8, 9, 10 and 11 by way of connectors to complete the mount assembly.

According to the present invention, the grid lead plate 7, which isobviously planar in contrast to the wire form conventionally used, iseffective not only to minimize the self-inductance thereby ensuring thatthe grid is perfectly earthed but also markedly to reduce thehigh-frequency ohmic loss occurring in the leads due to the skin effect.

Further, the grid lead plate 7, frame grid 13 and shield plate 12 areconnected to each other to form an electrically integral assembly whichis highly effective to shield the cathode and the anode from each otherwhile at the same time perfectly shielding the cathode and anode leadsfrom each other. Consequently, the formation of any capacity couplingbetween the input and the output is effectively prevented, thus theoperation of the electron tube is kept stable at high frequencies.

The ceramic wafer, having a characteristically small dielectric loss athigh frequencies, has further advantageous features that it allowsrelatively thick leads to be fitted therewith and brazed thereto unlikeconventional glass stems and that it can be hermetically sealed to glassas long as it has a coefiicient of expansion equal to that of theceramic. This makes it possible to seal the wafer to a miniature bulb 22of the conventional type to complete an electron tube as shown in FIG.3.

It will be appreciated from the foregoing that the electron tubeaccording to the present invention is not only free from thedifiiculties met with conventional miniature type electron tubes butalso easy to assemble and rigid in structure since all the electrodesare supported by a shield plate or by two mica sheets supported oppositeeach other by a shield plate, which in turn is supported by a grid leadplate.

Although one preferred embodiment has been described and shown herein,it is apparent to those skilled in the 3 art that many changes andmodifications may be made" therein without departing from the scope ofthe invention as defined in the appended claims.

What is claimed is:

1. A high-frequencyelectron tube'comprising a ceramic wafer, 21 gridlead plate sealed through. said wafer, a cathode pin and an anode pinsealed through said wafer respectively and shielded from each other bysaid grid lead plate, a cathode connected with said cathode pin by acathode conductor, an anode connected with said anode pin by an anodeconductor, and grid electrode means consisting of a frame grid securedto said grid lead plate and interposed between said cathode and saidanode operable to shield said cathode and said cathode conductor andsaid anode and said anode conductor from each other. I I g 2. Anelectron tube comprising an insulator wafer, a cathode pin andan anodepin respectively sealed through said wafer, a grid lead plate sealedthrough said wafer and separating said cathode pin and said anode pinfrom each other, a cathode, an anode, connecting means connecting saidcathode and anode with said cathode pin and said anode pin respectively,and a frame grid seured to said grid lead plate, interposed between saidcathode and cathode connecting means and said anode and anode connectingmeans. I e g g 3. A high frequency electron tube comprising a ceramicwafer,

a cathode pin and an anode pin sealed through said wafer respectively,

a grid lead plate interposed between said cathode pin and said anode pinand sealed through said wafer,

a frame grid means secured to said grid lead plate and extendinglongitudinally of the tube,

and a cathode and an anode connected with said cathode pin and saidanode pin respectively and provided on opposite sides of said frame gridmeans and mutually shielded therebetween by said frame grid means. 4. Ahigh frequency electron tube according to claim 3 in which said framegrid means is composed of a frame grid and a shield plate having anopening therein for electron beam passing, operatively connecting saidframe grid with said grid lead plate and supporting said cathode andsaid anode thereon in mutually insulated relationship. I

5. An electron tube comprising an insulator wafer, a cathode pin and ananode pin sealed through said wafer respectively, a cathode connectedwith said cathode pin by a cathode conductor, an anode connected withsaid anode pin by an anode conductor, a frame grid composed of a wiregrid and a frame and a grid lead plate sealed through said wafer andsupporting said frame grid thereon, said frame grid and said grid leadplate interposed between said cathode, said cathode conductor and saidcathode pin onone hand and said anode, said anode conductor and saidanode pin on the other in mutually shielded 1/1945 Bondley 3l3-2493/1958 Dailey 313-249 J OHN W. HUCKERT, Primary Examiner.

DAVID J. GALVIN, Examiner.

2. AN ELECTRON TUBE COMPRISING AN INSULATOR WAFER, A CATHODE PIN AND ANANODE PIN RESPECTIVELY SEALED THROUGH SAID WAFER, A GRID LEAD PLATESEALED THROUGH SAID WAFER AND SEPARATING SAID CATHODE PIN AND SAID ANODEPIN FROM EACH OTHER, A CATHODE, AN ANODE, CONNECTING MEANS CONNECTINGSAID CATHODE AND ANODE WITH SAID CATHODE PIN AND SAID ANODE PINRESPECTIVELY, AND A FRAME GRID SECURED TO SAID GRID LEAD PLATE,INTERPOSED BETWEEN SAID CATHODE AND CATHODE CONNECTING MEANS AND SAIDANODE AND ANODE CONNECTING MEANS.